Nitrate Selectivity and Transport Properties of a Novel Anion Exchange Membrane in Electrodialysis

Abstract

The synthesis and characterization of a novel heterogeneous anion exchange membrane with the aim of improving performance and increasing its nitrate selectivity was investigated. The lab-made membrane has a superior performance (higher nitrate selectivity, faster conductivity reduction and nitrate removal) at low voltages relative to that of a commercial membrane.As an ideal ion exchange membrane should have a high retention of co-ions and for some applications, selectivity between counter ions, the selectivity of the membrane was investigated in two ways: the selectivity between co-ions/counter-ions and the selectivity between two counter ions in electrodialysis. Activated carbon particles were used as an additive in order to enhance the properties and performance of the membrane. The retention of co-ions (selectivity of membrane towards co- ion/counter- ions), IEC, FIC and conductivity were enhanced through addition of activated carbon to anion exchange resin by a ratio of up to 1/100. A high conductivity reduction of feed solution was obtained at activated carbon to resin ratio of 1/100. However, the activated carbon has a negative effect on the membrane selectivity between counter ions (nitrate and chloride) and the highest selectivity was obtained in the lack of activated carbon. The lab made membrane has low resistance and it was found that at low voltages the lab-made membrane (without activated carbon) had a nitrate to chloride selectivity of 4.68 in electrodialysis.